Product details:

Acu-Arc 48" adjustable spline curve is made of incredibly flexible, shape-holding butyrate plastic that can be finger-shaped to any curve for extremely accurate drawings and layout. One edge is flat-to-surface for pencil, and the other side has a bead for ruling pen. Still manufactured by hand, these flexible curves have been used by architects, engineers, chiropractors, designers, draftsmen, artists, woodworkers, metal workers, surveyors, carpet installers, and law enforcement for over 45 years.